The composition of the wildlife of Madagascar reflects the fact that the island has been isolated for about 88 million years. The prehistoric breakup of the supercontinent Gondwana separated the Madagascar-Antarctica-India landmass from the Africa-South America landmass around 135 million years ago. Madagascar later split from India about 88 million years ago, allowing plants and animals on the island to evolve in relative isolation.
As a result of the island’s long isolation from neighboring continents, Madagascar is home to an abundance of plants and animals found nowhere else on Earth. Approximately 90 percent of all plant and animal species found in Madagascar are endemic, including the lemurs (a type of strepsirrhine primate), the carnivorous fossa and many birds. This distinctive ecology has led some ecologists to refer to Madagascar as the “eighth continent”,and the island has been classified by Conservation International as a biodiversity hotspot.
Madagascar’s isolation from other land masses throughout the Cenozoic Era has led to the evolution of a large proportion of endemic animal species and the absence of many taxa found on neighboring continents. Some of Madagascar’s animals appear to represent lineages that have been present since the breakup of Gondwana, while many others, including all of the nonflying native mammals, are descendants of ancestors that survived rare rafting or swimming voyages from Africa (likely aided by currents). As of 2012 it has over 200 extant mammal species, including over 100 species of lemurs, about 300 species of birds, more than 260 species of reptiles, and at least 266 species of amphibians. The island also has a rich invertebrate fauna including earthworms, insects, spiders and nonmarinemolluscs.
Lemurs have been characterized as “Madagascar’s flagship mammal species” by Conservation International. In the absence of monkeys and other competitors, these primates have adapted to a wide range of habitats and diversified into numerous species. As of 2012, there were officially 103 species and subspecies of lemur,39 of which were described by zoologists between 2000 and 2008. They are almost all classified as rare, vulnerable, or endangered. At least 17 species of lemur have become extinct since man arrived on Madagascar, all of which were larger than the surviving lemur species.
A number of other mammals, including the cat-like fossa, are endemic to Madagascar.
Over 300 species of birds have been recorded on the island, of which over 60 percent (including four families and 42 genera) are endemic.
The few families and genera of reptile that have reached Madagascar have diversified into more than 260 species, with over 90 percent of these being endemic (including one endemic family). The island is home to two-thirds of the world’s chameleon species, including the smallest known, and researchers have proposed that Madagascar may be the origin of all chameleons.
Endemic fish of Madagascar include two families, 15 genera and over 100 species, primarily inhabiting the island’s freshwater lakes and rivers.
Although invertebrates remain poorly studied on Madagascar, researchers have found high rates of endemism among the known species. All 651 species of terrestrial snail are endemic, as are a majority of the island’s butterflies, scarab beetles, lacewings, spiders and dragonflies.